The invention relates to a device for controlling an electric parking brake of a utility vehicle having an electronic control unit and a manual control unit, which communicates with the electronic control unit and by which driver's requests, which are dependent on the type of activation of the manual control unit can be transmitted to the electronic control unit. The electronic control unit is embodied such that it further processes signals of the manual control unit if the ignition of the utility vehicle is switched on.
The invention also relates to a method for controlling an electric parking brake of a utility vehicle having an electronic control unit and a manual control unit which communicates with the electronic control unit and by which driver's requests, which are dependent on the type of activation of the manual control unit are transmitted to the electronic control unit if the ignition of the utility vehicle is switched on.
Such devices and methods are becoming increasingly important in relation to the operation of utility vehicles. For the further development of the systems, emphasis is placed on various aspects, in particular the operating comfort and safety.
DE 103 53 056 A1 discloses a manual control unit in which great value is placed on the aforesaid aspects. With respect to safety, it is proposed in particular that it be possible to release the electric parking brake only if two activation elements, that is to say not only one activation element, are activated. Furthermore, the individual switches, which are activated by the operator control elements are configured in a redundant way in the manual control unit. Furthermore, mention is also made of the possibility of initiating a test function by use of the manual control unit, specifically releasing the braking a trailer in order to determine whether the parking brake of the towing vehicle alone is able to stop the entire train. The driver of a vehicle is advised to use this test function, in a particular when parking the vehicle on an incline.
Since an electric parking brake is actuated by an electronic control unit, it is necessary for the ignition of the utility vehicle to be switched on for the execution of functions in general. This is to be welcomed in terms of the safety of the utility vehicle since in this way it is impossible for any unintended actions, in particular release, to be brought about when the ignition is switched off. However, with respect to the operating comfort, the previous concept is capable of being improved. If, specifically, the driver forgets to close the parking brake during the switched on time of the ignition, it is no longer possible for him to subsequently close it when the ignition is switched off. He must first switch the ignition on again in order to carry out the desired action.
The invention is based on the object of making available a safe solution with respect to the control of an electronic parking brake, which solution entails improved operating comfort, in particular with respect to the dependence of the implementation of driver's wishes on the switched-on state of the ignition.
The invention builds on the prior art in that the manual control unit is embodied in such a way that in at least one type of activation it outputs a wakeup signal to the electronic control unit, and that the electronic control unit is also embodied in such a way that subsequent to the reception of a wakeup signal, it further processes at least one further signal of the manual control unit even when the ignition of the utility vehicle is switched off. It is, therefore, possible to interrupt the voltage supply of the electronic control unit with the ignition switched off. This is useful with respect to the electrical energy budget of the utility vehicle and, furthermore, is also appropriate in terms of safety technology since when the ignition is switched off, it is usually not possible for unintended actions to occur. However, it is also possible to provide that a wakeup signal on the basis of which it is possible to operate the parking brake despite the ignition being switched off can be output via the manual control unit.
This is useful, in particular, in the context in which the manual control unit is embodied such that it outputs a wakeup signal if an activation element for closing the parking brake is activated on the manual control unit. The driver can, therefore, still close the parking brake after the ignition has been switched off without further measures by virtue of the fact that he specifically activates the manual control unit in the conventional way, that is to say in the way in which he also uses it to close the parking brake when the ignition is switched on. During this operating procedure, a wakeup signal, which permits subsequent processing of a closing signal by the electronic control unit, is output automatically. Under certain circumstances it is, however, also desirable for the device according to the invention to be configured such that a release of the parking brake is made possible despite the ignition being switched off. In this case, the outputting of the wakeup signal is tied to the activation of the activation element for the release of the parking brake. This may be useful in particular in utility vehicles for conveying passengers; such a possible situation is, for example, when a vehicle comes to a standstill on a grade crossing. It is then highly advantageous if it is possible to bring about release of the parking brake independently of the switched-on state of the ignition or of the application of the ignition voltage to the electronic control unit. If the outputting of the wakeup signal is, however, tied to the outputting of the release signal, further safety measures have to be taken in order to avoid an unintended release of the parking brake from occurring.
It is in particular useful that the electronic control unit is embodied such that, when the ignition of the utility vehicle is switched off, it further processes precisely one further signal of the manual control unit subsequent to the reception of a wakeup signal. For the general case for which the present invention is configured, specifically that the ignition is switched off before the parking brake is closed, it is sufficient to permit the further processing of a single further signal after the reception of the wakeup signal by the electronic controller. Since the parking brake is closed after the further processing of the one further signal, the vehicle is therefore placed in a safe state and further signal processing is superfluous and undesired for technical safety reasons.
The invention is also usefully embodied in that the wakeup signal can be fed to a microcontroller via an analog/digital converter and a switching logic, in that, the electronic controller is configured such that, in addition to the wakeup signal, an “ignition on” signal can be fed to the switching logic. An output signal of the switching logic causes a switch for supplying voltage to the microcontroller to close when the wakeup signal and/or the “ignition on” signal are supplied.
The configuration of the present invention in terms of circuitry allows the wakeup signal and the “ignition on” signal to be treated with equal priority with respect to the switching logic. However, since the microcontroller is also informed of the presence of the wakeup signal, the electronic controller can ultimately operate with knowledge of the presence of this wakeup signal within the sense of the present invention, that is to say, for example, it can return to its voltageless state immediately after the closing process of the parking brake has been carried out. If the wakeup signal is suitably fed to the switch for supplying voltage to the microcontroller, it is, however, also possible to ensure independently of the microcontroller that only a limited time window is available after the outputting of the wakeup signal in order to bring about the further function, that is to say in particular the closing function.
In conjunction with the aforementioned switch for supplying voltage, it is also useful that the switch for supplying voltage to the microcontroller can be made to close as a result of an output signal of the microcontroller. This output signal of the microcontroller relates, in particular, to running on of the control device, as a result of which it is possible to carry out or to prevent certain functions in certain situations, even after the ignition has switched off. For example, the closing of the parking brake can be still permitted independently of the presence of the wakeup signal for several seconds after the switching off of the ignition.
The invention is based on the generic method in that the manual control unit outputs a wakeup signal to the electronic control unit in at least one type of activation, and in that, subsequent to the reception of a wakeup signal, the electronic control unit continues to further process at least one further signal of the manual control unit even when the ignition of the utility vehicle is switched off. As a result, the advantages and particular features of the device according to the invention can also be implemented within the scope of a method.
This is developed in a particularly advantageous way by virtue of the fact that the manual control unit outputs a wakeup signal if an activation element for closing the parking brake is activated on the manual control unit.
Furthermore, it is possible to provide that, when the ignition of the utility vehicle is switched off, the electronic control unit further processes precisely one further signal of the manual control unit subsequent to the reception of a wakeup signal.
The invention is particularly usefully used in that the further signal is a closing signal for closing the parking brake.
The method according to the invention is advantageously developed in that the wakeup signal is fed to a microcontroller via an analog/digital converter and a switching logic, in that, in addition to the wakeup signal, an “ignition on” signal is fed to the switching logic, and in that an output signal of the switching logic causes a switch for supplying voltage to the microcontroller to close when the wakeup signal and/or the “ignition on” signal are fed.
Furthermore, it is possible to provide that closing of the switch for supplying voltage to the microcontroller is brought about as a result of an output signal of the microcontroller.